For many years, various pieces of equipment have been developed for shearing thin pieces of wood from a larger block. Most of this equipment has been of the type which shears a single sheet or strip of wood from a block during each pass. Therefore, the stock material had to be repeatedly moved past the shearing knife or the knife past the block to obtain multiple strips. Despite this drawback for a number of uses, this type of equipment was considered desirable because despite its limitations, the amount of wood saved by eliminating the kerf of a saw more than offset the disadvantages of the system. This was particularly true when the resulting product was thin such as a few thousandths or a few hundredths of an inch in thickness. In cutting materials of this type, even the thinnest of saws reduced more than half of the material to saw dust thus making shearing economically attractive.
One of the most persistent problems in utilizing the shearing technique is that of the wood splitting ahead of the knife. When this happens, the thickness of the resulting product varies because the split will tend to follow the grain rather than a straight line. Further, the resulting surface condition of the product is much rougher than when the surface results from an actual cutting action. Another problem has been that of positively preventing the wood from twisting, particularly twisting upwardly as it is being sheared. This is also important to production of a product having uniformity of thickness. When it is attempted to produce more than one slice from the workpiece in a single pass, these problems are multiplied with the result that simultaneous multi-piece shearing has not been considered a commercially feasible means of slicing wood.